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Biomedical subjects

F Christ

Publications and source records attributed to F Christ.

At least 55 records · Page 3Linked to original sources
PubMed1997

Changes in subcutaneous interstitial fluid pressure, tissue oxygenation, and skin red cell flux during venous congestion plethysmography in men.

OBJECTIVE: Venous congestion plethysmography enables noninvasive assessment of microvascular filtration capacity (Kf) in limbs. However, increases in fluid filtration might alter the balance of Starling forces: for example, progressive increases in interstitial fluid pressure (Pi) would reduce net fluid flux, thus underestimating Kf. Furthermore, elevation of cuff pressure to values close to diastolic blood pressure, as used in the protocol, may be itself impair tissue perfusion with unknown effects on the microvascular parameters investigated. METHODS: Pi was measured in healthy volunteers (n = 14) with a modified "Wick in needle" technique during small (8 mm Hg) cumulative increases in venous pressure (0-95 mm Hg). Changes in the hemoglobin (Hb) concentration, oxygenated hemoglobin (HbO2) concentration and oxidized cytochrome aa3 concentration were assessed in the calf using noninvasive near-infrared spectroscopy. Skin red blood cell flux close to the strain gauge was evaluated by laser Doppler fluxmetry. RESULTS: Pi at control was -0.89 +/- 0.8 mm Hg and during elevation of venous pressure remained constant until a cuff pressure of 30 mm Hg was reached. It rose thereafter to 1.57 +/- 1.3 mm Hg (mean +/- SD). Skin red cell flux was significantly reduced when cuff pressure exceeded 30 mm Hg and following cuff deflation, evidence of reactive hyperemia was obtained. Hb concentration increased significantly as a result of venous pressure elevation. No change in either HbO2 or cytochrome aa3 concentration was observed as long as cuff pressure remained under diastolic blood pressure. CONCLUSIONS: The small increase in Pi together with an absence of impaired tissue oxygenation during the venous congestion plethysmography protocol described by Gamble et al. supports the contention that this protocol enables accurate assessment of filtration capacity.

Adult↗
PubMed1997

Microvascular fluid filtration capacity (Kf) assessed with cumulative small venous pressure steps and with various degrees of tilt.

Tilt procedures are frequently used to test central and peripheral cardio-vascular reflexes. We have previously used venous congestion strain gauge plethysmography for measurement of fluid filtration capacity (Kf) in human legs and have shown that, providing small cumulative venous congestion pressure steps are applied, venous congestion pressure can be increased to arterial diastolic pressure without activating peripheral vasoconstrictor mechanisms. We have also studied the effect of passive tilting on Kf and have shown that the procedure does not influence the measured value Kf indicating that passive tilting does not after the total surface area available for fluid filtration, but rather the blood flow in the microvessels of the tissue under study. In the present protocol we compared the fluid filtration (Jv) resulting from small (7-10 mmHg) cumulative pressure steps with those obtained by altering hydrostatic load with progressive increases and decreases of head down tilt of -8 degrees -15 degrees and -30 degrees, followed by a similar pattern of 15 degrees, 30 degrees and 70 degrees of head up tilt. The values of Jv obtained in response to these procedures were compared with those deduced from the relationship between fluid filtration and venous congestion pressure (Pcuff) obtained during the small cumulative pressure step protocol. It was reasoned that reflex activation, by the tilt induced pressure load, would cause a reduction in local blood flow and enhanced microvascular fluid extraction. The resulting local increase in colloid osmotic pressure would give rise to lower values of Jv than those predicted on the basis of the Kf slope.

Adult↗
PubMed1996

Binding, bending and cleavage of DNA substrates by the homing endonuclease Pl-SceI.

To characterize the interaction between the homing endonuclease PI-SceI and DNA, we prepared different DNA substrates containing the natural recognition sequence or parts thereof. Depending on the nature of the substrates, efficient cleavage is observed with a DNA containing approximatel 30 bp of the natural recognition sequence using supercoiled plasmids, approximately 40-50 bp using linearized plasmids and > 50 bp using synthetic double-stranded oligodeoxynucleotides. Cleavage of supercoiled plasmids occurs without accumulation of the nicked intermediate. In the presence of Mn2+, DNA cleavage by PI-SceI is more efficient than with Mg2+ and already occurs with substrates containing a shorter part of the recognition sequence. The requirements for strong binding are less stringent: a 35 bp oligodeoxynucleotide which is not cleaved is bound as firmly as other longer oligodeoxynucleotides. PI-SceI binds with high affinity to one of its cleavage products, a finding which may explain why PI-SceI hardly shows enzymatic turnover in vitro. Upon binding, two complexes are formed, which differ in the degree of bending (45 degrees versus 75 degrees). According to a phasing analysis bending is directed into the major groove. Strong binding, not, however, cleavage is also observed with the genetically engineered enzymatically inactive variant comprising amino acids 1-277. Models for binding and cleavage of DNA by PI-SceI are discussed based on these results.

Binding Sites↗
PubMed1996

Time discrete, near infrared photoplethysmography (NIRP) for non-invasive investigation of the volume pulse in man.

UNLABELLED: In pulse oximetry the principles of photoplethysmography are used for determination of heart rate and in some devices to also display the volume pulse. It has been suggested, that a more detailed analysis of the signal may allow quantitative analysis of peripheral hemodynamic events. We describe a new computer assisted time discrete analysis of the volume pulse, studying its reliability and the method s fundamental assumption of a linear relationship between changes in amplitude and changes in time sequences of the volume pulse. METHOD: In a finger clip two diodes emit near infrared (840 nm, NIR) and red light (640nm, RED) into the finger tip, where it is remitted mainly by the erythrocytes. 70 sec of recorded signal is filtered and the resulting volume pulse analysed off-line using a computer. On each volume pulse the time of the first (Tmax), the second maximum (time of dicrote, Td) and the duration of the volume pulse (Tp) are measured and the mean values displayed. In addition, the fundamental arterial oscillation Tag = Td - Tmax and all the above values in relation to Tp are calculated. Using NIRP, 54 healthy young volunteers (19 female, mean age 27.0 +/- 3.4 years) were studied and the individual mean values calculated from 960 measurements. The reliability during 10 repetitive measurements was investigated in 26 of the 54 volunteers. In 12 subjects 5 repetitive measurements were obtained from each finger and compared with each other. In 11 subjects the linear relationship between amplitude and time sequence was tested on > 30 000 single volume pulses. The finger clip photoelectrode was levelled with the right atrium in all measurements, skin close to the clip and room temperature were recorded. RESULTS: From the mean individual values the following time discrete values were calculated for the NIR signal (n = 41): Tp = 882.3 +/- 142.6 ms, Tmax = 214.8 +/- 28.3 ms, Td = 452.7 +/- 32.4 ms, Tdec = 667.4 +/- 133.6 ms, Tag = 237.9 +/- 36.3 ms, Tmax/Tdec = 0.34 +/- 0. 07, Td/Tdec = 0.7 +/- 0.11. For each parameter the individual standard deviation during 10 repetitive measurements (26 subjects) ranged between 2.2 and 6.1%. The time sequences found were not significantly different between the individual fingers. A linear relationship between changes in time sequence and changes in amplitude was found in all tested subjects (mean r = 0.96). CONCLUSION: These results show, that the values obtained with time discrete NIRP are highly reproducible and show an individual SD of less than 6.5% under steady state conditions. The linear relationship between time sequence and amplitude found in the present study has to be confirmed in further studies on patients with pathologies of the macro- and microcirculation.

Adult↗
PubMed1996

[Neurologic complications following total endoprothesis implantation of the hip under peridural catheter anesthesia].

This case report describes paralysis of the plantar flexors and extensors after a total hip replacement in a 33-year-old woman performed under epidural anaesthesia (PDA). Six years previously, the patient had undergone a bone marrow transplantation for chronic myeloid leukaemia. She had developed a deep vein thrombosis, a pulmonary embolus, and a severe graft-versus-host reaction of the skin, leading to markedly reduced mouth opening. The hip operation was performed using PDA following antithrombotic prophylaxis with low-molecular-weight heparin. Blood could initially be aspirated after advancing the PDA catheter, and a second puncture of the epidural space 1 segment higher enabled correct placement of the catheter. The patient received 500 ml Dextran 60 perioperatively and the operation was completed without any further problems. The PDA catheter was removed 2 h after the operation following the return of movement of both thighs. Fourteen hours after the completion of surgery it was noticed that the dressing over the epidural puncture site was bloodstained, the patient was incontinent, and complete loss of movement of the operated leg was present. An epidural haematoma was the suspected cause, but could not be definitely confirmed by a CT scan. Nevertheless, a laminectomy was undertaken to evacuate the suspected haematoma. As expected, tracheal intubation was only possible bronchoscopically. Intraoperatively, some low-grade epidural oozing at the level of the initial puncture site was observed, and a hemilaminectomy of 5 was performed. For the first time postoperatively, the bleeding time was measured and was markedly prolonged to 20 min (as described by Mielke, normal value up to 8 min). A coagulopathy was suggested, with the differential diagnosis of impaired platelet function. The paralysis of the plantar flexors and extensors and some sensory loss were still present 6 months after the operation. It remains uncertain whether the PDA in a patient receiving low-molecular-weight heparin resulting in a the suspected epidural haematoma was the cause of the neurological sequelae and in agreement with the consultant neurologist, we believe that a direct traumatic lesion of the L5/S1 segment or damage to the sciatic nerve are also likely causes of the symptoms. Undoubtedly, the lack of adequate postoperative neurological monitoring and the intraoperative administration of dextran despite the known epidural vascular lesion deserve criticism. This case report demonstrates the often complex development of neurological complications after nerve blocks, where a definite cause can frequently not be determined.

Adult↗
PubMed1995

Investigating the origin of cyclic changes in limb volume using mercury-in-silastic strain gauge plethysmography in man.

1. Vasomotion, a phenomen frequently observed in skeletal muscle microcirculation, has been observed under physiological conditions and found enhanced during critical reduction of tissue perfusion due to hypoxic hypoxia, haemorrhage and local hypotension. We used a computer assisted non-invasive plethysmographic method to investigate periodic changes of limb volume (volumotion), which we previously found in critically ill patients. The current study was designed to investigate the origin of volumotion. 2. Simultaneous recordings of limb circumference of both calves were obtained. In patients with peripheral vascular disease and patients with minor surgery the cross-correlation with spontaneous breathing was investigated. In patients who had undergone major abdominal or vascular surgery we analysed for cross-correlations between MSG plethysmography signals of both legs and changes in central venous, arterial and ventilation pressures. In this group the effects of positive-pressure ventilation and positive end-expiratory pressure (PEEP) were also studied. 3. No ventilation-related volumotion was observed during spontaneous breathing. During positive-pressure ventilation a ventilation-related peak was found in the Fourier transform in agreement with the ventilation frequency applied. The amplitude of ventilation-related volumotion decreased significantly after a pressure cuff applied to the thigh was inflated above central venous pressure. We observed a significant increase in the amplitude of ventilation-related volumotion when PEEP was applied. 4. Ventilation-related volumotion showed significant cross-correlation between both legs. Slow wave volumotion (0.5-7 cycles min-1) was frequently observed, but always appeared unilaterally. Whilst we looked for correlations between slow wave volumotion and changes in central venous pressure and arterial blood pressure, respectively, significant cross-correlation with the MSG plethysmography recordings was only observed at the frequency of the positive-pressure ventilation. 5. The fact that periodic changes of limb circumference matching the frequency of the positive-pressure ventilation were detectable with the MSG plethysmography system demonstrates that small volume changes (less than 0.02 ml (100 ml tissue)-1) can be assessed using this system. As slow wave volumotion was observed unilaterally and revealed no correlation either with breathing, ventilation or arterial and central venous pressure, we suggest that slow wave volumotion is a local event most likely reflecting arteriolar vasomotion.

Aged↗
PubMed1994

The expression of GAP-43 and synaptophysin in the developing rat retina.

We have undertaken a detailed study of the expression of GAP-43 and synaptophysin immunoreactivity in the developing postnatal rat retina. We found that these two 'presynaptic' proteins have quite different expression patterns. GAP-43 was first expressed in the optic nerve and the optic fiber layer of the retina, where it disappeared between the 8th and 16th postnatal day. From the 5th postnatal day on, GAP-43 also appeared in the inner plexiform layer, where it was present in three distinct bands. This expression changed little in postnatal development and persisted in the adult retina. GAP-43 was not detected in the outer plexiform layer of the retina. Synaptophysin was absent from the optic nerve and optic fibers at all postnatal stages. It was first expressed in the developing outer plexiform and, with reduced intensity, in the outer nuclear layer between postnatal days 2 and 5. In the inner plexiform layer, synaptophysin could be first detected between postnatal days 8 and 12. The intensity of staining increased during postnatal development in both plexiform layers. The developmental sequence of synaptophysin expression can be correlated with the maturation of presynaptic terminals of photoreceptors and bipolar cells. The rather complex pattern of GAP-43 expression is not easily compatible with a single model of GAP-43 function, and suggests diverse functions of this molecule in the retina.

Animals↗
PubMed1993

A reassessment of mercury in silastic strain gauge plethysmography for microvascular permeability assessment in man.

1. We have used non-invasive mercury in a silastic strain gauge system to assess the effect of pressure step size, on the time course of the rapid volume response (RVR) to occlusion pressure. We also obtained values for hydraulic conductance (Kf), isovolumetric venous pressure (Pvi) and venous pressure (Pv) in thirty-five studies on the legs of twenty-three supine control subjects. 2. The initial rapid volume response to small (9.53 +/- 0.45 mmHg, mean +/- S.E.M.) stepped increases in venous pressure, the rapid volume response, could be described by a single exponential of time constant 15.54 +/- 1.14 s. 3. Increasing the size of the pressure step, to 49.8 +/- 1.1 mmHg, gave a larger value for the RVR time constant (mean 77.3 +/- 11.6 s). 4. We propose that the pressure-dependent difference in the duration of the rapid volume response, in these two situations, might be due to a vascular smooth muscle-based mechanism, e.g. the veni-arteriolar reflex. 5. The mean (+/- S.E.M.) values for Kf, Pvi and Pv were 4.27 +/- 0.18 (units, ml min-1 (100 g)-1 mmHg-1 x 10(-3), 21.50 +/- 0.81 (units, mmHg) and 9.11 +/- 0.94 (units, mmHg), respectively. 6. During simultaneous assessment of these parameters in arms and legs, it was found that they did not differ significantly from one another. 7. We propose that the mercury strain gauge system offers a useful, non-invasive means of studying the mechanisms governing fluid filtration in human limbs.

Arm↗
PubMed1993

Pneumocystis carinii infections in HIV-infected hemophiliacs during aerosolized pentamidine prophylaxis.

The frequency, presentation, diagnosis and clinical course of Pneumocystis carinii infections (PCI) were studied during aerosolized pentamidine prophylaxis (AP) and its impact on the spectrum of AIDS-related and other pulmonary infections in HIV-infected hemophiliacs. We conducted an open study on primary (PP) and secondary (SP) AP. Breakthrough P. carinii infections (BPCI) and other infectious complications were analyzed retrospectively. Hemophiliacs without prior P. carinii pneumonia (PCP) who had been reluctant to any prophylaxis and who developed PCP served as control group. Statistical analysis of the efficacy of prophylaxis was performed by calculating confidence intervals of binomial p. Of 73 hemophiliacs (56 on PP and 17 on SP) 10 developed BPCI (7 in PP and 3 in SP) during a mean observation time of 14.9 months (range 0.5-30); total 13.6% (6.7%; 23.7%), PP 12.5% (5.1%; 24%), SP 17.6% (3.7%; 43.4%), confidence intervals at a level of 95%. Three BPCI presented atypically with cavitation (1), pneumothorax (2), Pneumocystis pleuritis (1), dissemination (2) as compared to none in the control group. Sensitivity of bronchoalveolar lavage (BAL) was 88.9%, specificity 100% (both 100% in the control group). PCP was the leading AIDS manifestation (21.3%), CNS manifestations taken together were more frequent (36.2%). Bacterial pneumonia was the most frequent respiratory infection. One patient of the study group with recurrent pneumothorax possibly died of BPCI as compared to no BPCI-related deaths in the control group. Efficacy of prophylaxis in hemophiliacs was comparable to other risk groups. AP alone may be insufficient for the control of PCI in patients with long-term profound immunodeficiency, especially in SP. 30% of BPCI presented atypically.(ABSTRACT TRUNCATED AT 250 WORDS)

AIDS-Related Opportunistic Infections↗
PubMed1993

Pneumocystis carinii pneumonia presenting as an upper lobe cavity after aerosolized pentamidine prophylaxis in an HIV-infected patient.

We describe an atypical diagnostic feature of a breakthrough Pneumocystis carinii pneumonia (PCP) during primary prophylaxis with aerosolized pentamidine. Our case disclosed infiltrates restricted to the left upper lobe. After 2 weeks a solitary cavity developed. Diagnosis was easily established by bronchoalveolar lavage when performed in the affected segment bronchus. Cavitation clearly demonstrated localized infection, with tissue destruction as one main pathogenetic pattern of a breakthrough PCP during aerosolized pentamidine prophylaxis.

Adult↗
PubMed1993

[Microvascular monitoring using mercury in silastic strain gauge plethysmography (MSG)].

Mercury in silastic strain gauge plethysmography (MSG) is a noninvasive method for assessing microvascular parameters in peripheral limbs. MSG allows measurement of capillary filtration coefficient (Kf), isovolumetric venous pressure (Pvi), venous pressure (Pv) and arterial inflow (Qa) into the limb, respectively. We used MSG in combination with invasive monitoring techniques (pulmonary artery flotation catheters and arterial catheters) to study 36 critically ill patients in either hemorrhagic or septic shock. We observed marked increases in Pvi in both patient groups which correlated with outcome. On admission, both groups showed elevated values for Pvi, survivors 37.7 +/- 2.6, nonsurvivors 33.7 +/- 3.5 mm Hg (mean +/- SEM) when compared with a control group of young healthy students (22.1 +/- 0.82 mm Hg). Survivors showed a decrease in Pvi to 27.3 +/- 1.7 mm Hg, whereas in nonsurvivors Pvi increased to 39.5 +/- 3.0 at the last measurement taken. The changes in Pvi depended on the resuscitation regime used. On admission, patients requiring only fluid replacement (F) had a lower Pvi (31.3 +/- 2.9 mm Hg) than patients needing inotropic support with dobutamine (D, Pvi = 38.2 +/- 2.4 mm Hg) to fulfill our therapeutic goals (DO2 > 550 ml.min-1 x m-2, VO2 > 150 ml.min-1 x m-2 and mixed venous lactate < 1.5 mmol/l). After treatment Pvi did not change significantly in the F group (31.3 +/- 1.8), the D group however showed a significant decrease in Pvi to 25.4 +/- 2.42, which did not differ from the normal value. We regard Pvi as an indicator of insufficient microvascular flow.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

[Cryptogenetic ascites. Attempts at original pathophysiologic explanation of a monomorphic sonographic image pattern].

In 15,645 consecutive ultrasound examinations of the abdomen (1986 to 1988), free fluid in the peritoneal cavity was found in 247 patients by internal trial during 397 sessions (= 2.5%). Most frequent basic diagnosis for the reason of this symptom were tumorous diseases (99 patients corresponding to 40.1%), cirrhosis of the liver (52 patients corresp. to 22.1%) and heart failure (31 patients corresp. to 12.6%, among these complex gayprooft myocardial insufficiency 24, right heart failure 7). Ovarian cysts or cystomas (7), acute/chronic-recurrent pancreatitis (6), Crohn's disease (3), infections (3), rheumatoid disorders (3), nephrotic syndrome (2), and extra-uterine pregnancy (2) were more rarely represented. In 23 patients (corresp. to 9.3%) the cause of an ascites remained obscure. Among these, a high prevalence of the female sex in the premenopausal age was remarkable with a score of 20:3 (statistically significant difference in terms of the other patients of our group). This observation suggests that an ovarian factor plays a role in the development of ascites in the absence of other evident causes. The literature implies that endometriosis is rather prominent, followed by oligosymptomatic infections or inflammatory diseases.

Adolescent↗
PubMed1992

[A comparison of the value of magnetic resonance tomography and computed tomography in Nelson syndrome patients].

The hypophyses of 13 patients with Nelson syndrome following bilateral adrenalectomy were examined by MRI and CT. Diffuse enlargement of the hypophysis was demonstrated in 8 patients by CT and in 9 by MRI. Compared with CT, MRI provides better demonstration of tumour development, such as abnormal convexity of the cranial margin of the hypophysis (MRI 4/13, CT 1/13), displacement of the infundibulum (MRI 4/13, CT 0/13) or optic chiasm (MRI 2/13, CT 0/13). MRI also provides diagnostically important differentiation between scar tissue and recurrence of tumour following hypophysectomy (MRI 1/3, CT 0/3) and more accurate demonstration of infiltration of the cavernous sinus (MRI 4/13, CT 2/13). CT is superior only in showing the floor of the sella. MRI is the method of choice for imaging in cases of Nelson syndrome.

Adrenalectomy↗
PubMed1992

Mercury in silastic strain gauge plethysmography for the clinical assessment of the microcirculation.

We have used the mercury in silastic strain gauge plethysmography (MSG) system, which is wholly non-invasive, to obtain values (mean +/- s.e.m.) for the following parameters in the legs of supine control subjects: venous pressure (Pv) 9.89 +/- 0.88 mmHg, vascular compliance (Comp) 3.50 +/- 0.29 ml 100 g-1 mmHg-1 x 10(-2), microvascular hydraulic conductivity (Kf) 4.10 +/- 0.16 ml min-1 100 g-1 mmHg-1 x 10(-3) and isovolumetric venous pressure (Pvi) 22.12 +/- 0.82 mmHg. On passive foot-down tilting of control subjects through about 45 degrees, both Pv and Pvi rose to 28.00 +/- 2.33 and 36.58 +/- 2.29 mmHg respectively. The increases in both parameters were highly significant, P < 0.0001. We found that the time course of the vascular compliance component was short if small pressure steps were used. The value increased markedly if large steps were used. We also observed that none of the microvascular parameters studied in the arms differed from those in the legs of the same subjects. We observed that the mean value Kf in the arms of 12 young, non-neuropathic diabetics (9.08 +/- 6.12 x 10(-3)) was significantly greater than that of age and sex-matched controls (P < 0.001). Studies on 14 venous ulceration patients indicated that the values for Kf and Pv were unchanged, whilst those of vascular compliance (5.60 +/- 0.58 x 10(-2) ml 100 g-1 mmHg-1) and Pvi (37.30 +/- 2.25 mmHg) were significantly greater than those found in age-matched controls (P < 0.002 and 0.001, respectively). We feel that Pvi is a useful index of microvascular perfusion. We attribute the pressure-dependent difference, in the time course of the vascular compliance response, to the veni-arteriolar reflex. We feel that the pressure dependency of this response might form the basis for the assessment of peripheral autonomic neuropathy. We believe that the MSG system offers a means of monitoring the development of pathologies resulting from microvascular under-perfusion and, of course, the improvement in response to therapeutic interventions.

Adult↗
PubMed1991

[Spontaneous regression of liver metastases in neuroendocrine tumors of the abdomen].

In six patients with hepatically metastasised gastrointestinal tumours of neuro-endocrinal origin, including one each islet cell carcinoma and gastrinoma of the pancreas, one cloacogenic carcinoma (a rare type of anal cancer), and three carcinoid tumours of the small bowel, spontaneous liquefaction inside echogenic liver metastases was demonstrated by ultrasound. The hepatic lesions were classified as being of "bull's-eye-" shape without "badge" pattern. Chemotherapy had no effect on their ultrasonographic imaging. With regard to our observations, liquefying processes were far more common in these well-differentiated tumour metastases than in poorly differentiated fast-proliferating malignancies (about 1:40). Assessment of liquefaction, however, has obviously no influence on the prognosis of progress speed. Ultrasonographic differential diagnosis includes focal inflammatory disease of the liver, if there is no evidence of a primary tumour.

Carcinoid Tumor↗